The invention relates to an optical measurement module for measuring angles and/or distances and to an optical measurement transmitter.
For technical applications which require angle or distance measurement it is often expedient to incorporate angle and distance measurement systems into existing instruments. Hitherto, this has predominantly been carried out by using so-called closed transmitter systems, which include a scale embodiment and an operational measurement head. These closed transmitter systems have their dedicated mounting consequently integrated therein and have to be fastened in an appropriate way through the use of coupling devices to the object to be measured. The construction of these measurement transmitters is voluminous and expensive as a result of the dedicated mounting. Furthermore, fixing these measurement transmitters, for example to the ends of shafts in the case of angle measurement transmitters, is often a disruptive procedure when these transmitter systems are installed. The transmitter systems are therefore complicated in terms of production and mounting.
Solutions using so-called incorporated transmitters (without a dedicated mounting), have so far been used only in the case of low angular resolutions and clean environmental conditions, and have not become generally accepted. Although the bearings are dispensed with, the inadequate precision mounting, the complicated adjustment, the required clean rooms, the problematic illumination and imaging conditions have been a hindrance and have not permitted any use. The incident-light illumination desired in the case of incorporated transmitters needs complicated, expensive and sensitive surface structures (defractive optical structures) for the embodiments of the scale, in order to achieve an adequate image, since, as a result of the necessary obliquely incident illumination, no mirror-reflective substrate surfaces are permitted. These specific optical surfaces are complicated and can be implemented only with expensive tools, and are very sensitive.
It is accordingly an object of the invention to provide an optical measurement module for a high-resolution angle and/or distance measurement transmitter, and such a measurement transmitter which overcome the above-mentioned disadvantages of the heretofore-known measurement modules and measurement transmitters of this general type and wherein the measurement module can be incorporated in an integrated manner.
With the foregoing and other objects in view there is provided, in accordance with the invention, in combination with a scale embodiment an optical measurement module for measuring angles and/or distances for determining a position of the optical measurement module with respect to the scale embodiment, the optical measurement module includes:
a detection device for detecting light;
an imaging device for imaging a part of the scale embodiment onto the detection device; and
a light guiding device for guiding incident light to the scale embodiment and for guiding light coming from the scale embodiment to the detection device.
In other words, the optical angle and/or distance measurement module according to the invention for measuring its position with respect to a scale embodiment includes a device for light detection and a device for imaging a part of the scale embodiment onto the detection device. It also contains a device through the use of which, firstly, incident light can be led onto the scale embodiment and, secondly, light coming from the scale embodiment can be led to the detection device.
With the objects of the invention in view there is also provided, an optical measurement transmitter, having a sensing head including an optical measurement module for measuring angles and/or distances; a scale embodiment; the sensing head determining a position of the optical measurement module with respect to the scale embodiment; and the optical measurement module including a detection device for detecting light, an imaging device for imaging a part of the scale embodiment onto the detection device, and a light guiding device for guiding incident light to the scale embodiment and for guiding light coming from the scale embodiment to the detection device.
In other words, the optical measurement transmitter according to the invention includes a sensing head and a scale embodiment that can be moved relative to the sensing head, the sensing head containing an optical angle and/or distance measurement module according to the invention.
As a result of the measures according to the invention, the patterns on virtually all substrate surfaces can be registered by the virtually xe2x80x9creflectivexe2x80x9d or diffusely reflecting planar structures, which can be applied simply by using known lithographic etching processes, printing and/or laser-writing processes. Thus, even structures written in a simple way, for example by a beam, on shafts and drums are possible, and particularly inexpensive angle and/or distance measurement systems can be implemented.
According to another feature of the invention, a light source is provided for producing the incident light.
According to yet another feature of the invention, the light source is a light-emitting diode or a laser diode.
According to a further feature of the invention, the scale embodiment has a surface area. An intermediate part is provided for maintaining a given distance between the optical measurement module and the scale embodiment in a direction perpendicular to the surface area of the scale embodiment and/or the intermediate part permits a relative movement of the optical measurement module with respect to the scale embodiment.
According to another feature of the invention, the intermediate part is a sliding surface.
According to yet another feature of the invention, a first module element and a second module element are provided, the first module element containing the detection device and the second module element containing the intermediate part for permitting the relative movement.
According to another feature of the invention, a positioning device maintains a defined position of the optical measurement module with respect to the scale embodiment in a direction of an areal extent of the scale embodiment.
According to another feature of the invention, the optical measurement module has a relative position with respect to the scale embodiment, the relative position is defined by an absolute value and an incremental value. The detection device has light-sensitive areas for registering both the absolute value and the incremental value of the relative position.
According to a further feature of the invention, the detection device supplies output signals. An electronic device processes the output signals from the detection device for forming a total absolute value of a relative position of the optical measurement module with respect to the scale embodiment.
According to another feature of the invention, the imaging device images a part of the scale embodiment telecentrically onto the detection device. According to yet another feature of the invention, the imaging device includes an imaging lens and an aperture stop acting as an exit pupil or an aperture diaphragm.
According to a further feature of the invention, a supporting body is formed of plastic, and the imaging device is integrated in the supporting body.
The further configurations of the invention in particular permit the high-resolution incorporation of precision transmitters, in which mechanical tolerances during incorporation and operation are compensated. An intermediate part which slides easily and is flexible not only contributes to the simple mounting or maintenance of the incorporated transmitter; instead, not inconsiderable mechanical deflections of the scale embodiment (e.g. motor shaft ends or rules) are automatically compensated for. In addition, according to the invention, the intermediate part is configured in such a way that a plastic optical system created in a cost-effective manner is protected to the greatest possible extent against vapors, dust, etc. on a sensitive lens surface.
The configuration according to the invention, allows a cost-effective production of the measurement head and the scale embodiment, and of the high-resolution measurement systems, since the incident-light illumination permits simple labelling, and the mounting and incorporation tolerances, as well as dirty environmental influences, are coped with.
The measurement module according to the invention can be used both in xe2x80x9copenxe2x80x9d measurement transmitters, the measurement module preferably moving in a sliding manner on the scale embodiment, and in xe2x80x9cclosedxe2x80x9d measurement transmitters. The measurement module is preferably incorporated in the measurement transmitter in such a way that it maintains a defined distance from the scale embodiment, which is likewise incorporated.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an optical angle and/or distance measurement module, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.